GNGTS 2021 - Atti del 39° Convegno Nazionale

99 GNGTS 2021 S essione 1.2 REPROCESSING THE 1978 ENI-ENEL VINTAGE SEISMIC REFLECTION PROFILES OF CAMPI FLEGREI: PRELIMINARY RESULTS. P.P. Bruno 1, 2 1 Dipartimento di Scienze della Terra, Ambiente e Risorse, Università di Napoli Federico II, Italy 2 Istituto Nazionale di Geofisica e Vulcanologia, Italy During the year 1978 seven seismic reflection profiles acquired by a joint venture between Agip and Enel to explore for geothermal resources in the Campi Flegrei caldera. These vintage profiles are therefore affected by all the technological limitations existing at that time; for instan- ce, they were acquired with a very sparse number of shot points consisting of explosive sources and with a low number of channels; moreover, they are characterized by a low bandwidth and a low dynamic range and, overall, by low signal-to-noise ratio, especially when the profiles come closer to the volcanic edifices. Nevertheless, these profiles cross areas where today, due to the high-level of urbanization, environmental issues and the increased volcanic hazard it would be impossible to acquire new seismic reflection data: Therefore with all their limitations they repre- sent a precious information that, tied to the many exploration wells with geophysical logs, can contribute to better define the structure of Campi Flegrei Caldera and improve our understan- ding of the geometric and stratigraphic relationships between the caldera and the Volturno Plain. Presented here are the preliminary results of a reprocessing phase aimed at improving the quality of those profiles. Given the characteristics of the acquisition geometries and the quality of the data, the use of up-to-date seismic reflection processing schemes, such as pre-stack depth imaging, reflection tomography and full-waveform inversion are precluded. The reprocessing was therefore designed based on the available quality, with the application of algorithms that ope- rate in the time domain. On a preliminary profile which is representative of the overall dataset quality, first a crooked line geometry was assigned, followed by the application of a conventional common-midpoint (CMP) processing and of a less conventional common reflection surface (CRS) processing. CRS stacking operator, being not based on the estimation of a stacking velocity, which is problematic in this environment and on those data, can improve the quality of the seismic ima- ging. The CMP and CRS stacks underwent a post-stack time migration and depth conversions with vertical stretching. Velocity estimation along the profile was made by a tomographic inversion of the first arrivals.